nghttpd, tiny-nghttpd: No need to check existence of stream

The stream existence is guaranteed by library as of
cc03a12b.

examples/tiny-nghttpd.c

@@ -660,17 +660,11 @@ static void stream_error(connection *conn, int32_t stream_id,
 
 static int send_data_callback(nghttp2_session *session _U_,
                               nghttp2_frame *frame, const uint8_t *framehd,
-                              size_t length, nghttp2_data_source *source _U_,
+                              size_t length, nghttp2_data_source *source,
                               void *user_data) {
   connection *conn = user_data;
   uint8_t *p = conn->buf.last;
-  stream *strm;
-
-  strm = nghttp2_session_get_stream_user_data(session, frame->hd.stream_id);
-
-  if (!strm) {
-    return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
-  }
+  stream *strm = source->ptr;
 
   /* We never use padding in this program */
   assert(frame->data.padlen == 0);

src/HttpServer.cc

@@ -1218,12 +1218,6 @@ int send_data_callback(nghttp2_session *session, nghttp2_frame *frame,
                        const uint8_t *framehd, size_t length,
                        nghttp2_data_source *source, void *user_data) {
   auto hd = static_cast<Http2Handler *>(user_data);
-  auto stream = hd->get_stream(frame->hd.stream_id);
-
-  if (!stream) {
-    return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
-  }
-
   auto wb = hd->get_wb();
   auto padlen = frame->data.padlen;